Circulating immune complexes, complement activation kinetics and serum sickness following treatment with heterologous anti-snake venom globulin.

Consecutive serum and plasma samples, from a patient receiving 100 ml polyvalent horse anti-venom globulin after a rattlesnake bite, were analysed for circulating immune complexes (IC) and activation of complement factors. IC were determined by two independent methods, a complement consumption assay and a Clq-binding assay. Rapidly rising levels of complement-fixing circulating IC were detected as early as 4--5 days after the serum treatment and distinct IC-activity was recorded in both assays on day 8 when clinical symptoms of serum sickness were observed. The IC remained in circulation for at least 5 weeks. Signs of intravascular C-activation in the form of low C3, C4 and C5 values was noted on day 1 after treatment. Factor B was demonstrable 3--4 days after the snake bite and this factor and C3c attained a peak around day 8, just before maximal suppression of native C3 and C4. 14 days after the globulin treatment C3c and B were declining rapidly while C3 and C4 approached normal values first 36 days after treatment. An increase in heterophilic antibodies to sheep erythrocytes was observed after treatment with anti-venom globulin.